Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 212348 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
648 PM CDT Mon May 21 2018

Issued at 640 PM CDT Mon May 21 2018

See below for an aviation forecast discussion for the 00Z TAFs.


.SHORT TERM...(This Evening through Tuesday Afternoon)
Issued at 347 PM CDT Mon May 21 2018

A few isolated light showers in the east are expected to dissipate
by evening as an upper level low pressure trough moves east.
Otherwise, the issue tonight will be how much of the low clouds
across the east break up/move out into this evening. If they dont,
they will likely stay in much of the night. If they break up or move
out, it looks like with light southeast winds through the night and
high low level moisture, expect more stratus and fog to develop
again later tonight and remain into Tuesday morning. Thus, kept the
far east mostly cloudy with some patchy to maybe areas of fog
developing. With upper level ridging building in Tuesday and drier
air, expect mostly sunny skies. The surface pressure gradient will
tighten up a little, especially out west with a bit higher southeast
winds than today.

.LONG TERM...(Tuesday Evening through Monday)
Issued at 347 PM CDT Mon May 21 2018

Not much has changed from previous forecast runs in the extended
term. The main highlights will be the warm temps expected and the
periodic chances for showers and thunderstorms. The upper level
pattern will feature a ridge sliding through our region and into the
Upper Midwest/W. Great Lakes region at the beginning of the period.
An upper level trough/low is progged to be over the Great Basin and
shift NNE with time. At the sfc, our cwa will be in between a
departing high to the east and a lee side broad area of low pressure
west. Southerly flow will allow a moist airmass to remain in place.
This, in combination with increasing instability and some upper lvl
s/w energy rotating out of the main trough in the west will provide
focus for shower and thunderstorm activity across the region. This
pattern looks to remain consistent enough Wednesday through Thursday
night to keep periodic chances for thunderstorms in the forecast.

By the end of the work week, the pattern will begin to shift. The
upper trough slides north into southern Canada pulling north the
broad sfc low across the western Dakotas. The upper trough is
progged then to move east across southern Canada which will give us
a more W/NW flow allowing the sfc low and assoc frontal boundary to
move through. Models have some slight timing differences with this
fropa anywhere from earlier on Friday to later Friday/early
Saturday. However, anticipate this should iron itself out with
time as the week progresses. Temperatures look to remain well
above normal for late May through the period. It should feature
some fairly warm to hot daytime periods with mild, more humid
overnights. Even with the fropa late in the week, temps look to
stay above normal.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 640 PM CDT Mon May 21 2018

KPIR/KMBG and KABR should be VFR for pretty much the entire TAF
valid period. There could be some sub-VFR radiation/ground fog
developing toward sunrise at KABR. But that`s a fairly low
probability scenario, so, for now, will leave out the mention at
KABR and monitor satellite/webcam/observation trends into the

KATY, however, remains socked in by low (MVFR) clouds. Should
these low clouds clear off by 02-03Z, expect the window of VFR to
be short lived, as clear skies/light southeast winds and copious
amounts of surface/near surface high-moisture-content air to
promote IFR fog and/or low stratus clouds overnight into Tuesday
morning. Eventually, KATY should see a return to VFR conditions
during the day on Tuesday.




LONG TERM...Vipond
AVIATION...Dorn is the U.S. government's official web portal to all federal, state and local government web resources and services.